Knowledge of the three-dimensional structure of biologically relevant molecules is having increasing impact in biology and medicine, and particularly in AIDS research. X-ray crystallography has been an especially important method for determining these structures, and computational biology has been very important for visualizing and interpreting these structures. Much of structural biology has been restricted to experts working in these areas. we propose in the Structural Biology core to establish a resource that will broaden the availability of these powerful tools to other researchers within the CR-CFAR. The core will provide assistance with protein production, purification, and crystallography, as well as with computer modeling of structures.